Generally, a computer (e.g. a traditional microcomputer) is used to load applets. The applet to be loaded is, for example, stored on a hard disk of the computer. A resident program in the computer, known as the “Loader” receives in input a file containing the applet and converts it into a set of commands that it sends to the SIM card.
These commands can be sent in two main ways:                locally, from a smartcard reader connected to the computer.        remotely, for example by using the technology known as Over The Air (O.T.A.) in GSM terminology.        
These methods present several disadvantages.
Firstly, the SIM card is inserted in the smartcard reader of the computer used for loading. It can be seen immediately that this methods presents the disadvantage of requiring specific hardware. At least, the subscriber, holder of the SIM card, must physically go to a place where this type of hardware is available.
As regards the second method, it is worth pointing out that digital data is generally transmitted via the Short Message Service (SMS) technology (GSM-Data Service) in compliance with the two standards ETSI 03.40 and ETSI 03.48. Generally, the maximum length of useful in these messages is 160 septets or 140 octets, depending on the applications. Although with current technology, smartcards can only store programs requiring relatively a limited amount of memory, as is the case with the applets, they often come in the form of files occupying about 10 kB. Clearly, it would take about 80 messages to send a file of this length. It must also be pointed out that with transmissions implementing OTA technology, the security and/or reliability rates are not very high. In particular, especially when a set of SIM cards must be updated with data, even identical, the process has to be repeated for each mobile telephone, since the links between a remote server and a mobile telephone are “point to point”. Consequently, the above-mentioned method is, in practice, extremely complicated and possibly even impossible to implement.
Since the mobile telephones concerned by the invention are dual slot type, as pointed out earlier, one possible method could have been to use the auxiliary reader to load applets in the SIM card inserted in the main reader. An obvious solution would in fact be to implement a loader program in the subscriber's SIM card. The code of the applet to be loaded could then be stored in another smartcard which could be inserted in the auxiliary reader.
The loader program in the SIM card could then transmit one or more proactive command(s) in order to read the code of the applet to be loaded. Once the program has read the applet code, it can then load it using a suitable means.
Initially, this method seems to offer advantages:
1) The loader program of the SIM card is compatible with the card itself since stored in it;
2) The auxiliary smartcard containing the applet code does not need to comply with the Sim Toolkit standard.
However, this method presents significant disadvantages:
1) Since the loader program takes up a non-negligible amount of space in the SIM card, there is less space for the applets which have to be stored there. Even though the capacity of the memories used on smartcards has significantly increased over the last few years, it remains relatively limited for this type of application.
2) This solution cannot be considered using the present technology, since:                It is impossible to send loading commands. The commands to be sent by the application to the operating system in the SIM card are in fact specified in the standard ETSI 03.19. Loading commands cannot be sent under this standard.        In addition, the applet cannot request the mobile telephone to send commands to the card it hosts.        
The current standards would therefore have be modified in order to consider this type of operation.
It is known from the european patent application EP 0 869 691 a mobile phone in which the SIM card communicates with an external component. The SIM card behaves as a gateway between the external component and the GSM network and/or the mobile phone so that the external component controls completely the mobile phone. The modified functionalities are transferred through applets via the SIM card to the external component.
It is also known from the international patent application WO 00/154530 a system allowing to program a set of selectable optional features into the memory of a cellular telephone independtly of the main program. The systems is constituted of a programmer and a port. The programmer located outside the housing of the telephone sends the set of selectable optional features to the port for storage in the memory.
The invention aims to overcome the disadvantages of the methods and devices of the known state of the art, some of which have just been described.
The purpose of the invention, for a mobile device of type including two card readers, is to define a method for the administration of digital data, applications and/or simple data, stored on a first smartcard, called subscriber or SIM smartcard, inserted in a first smartcard reader, called the main reader, via a second smartcard, called administration card, inserted in a second smartcard reader, called auxiliary smartcard reader.
The method according to the invention can be used not only to add one or more applets in the SIM card, i.e. to load applets, but also provides
true management or administration of digital data, applications and/or simple data, stored in it. Apart from loading digital data in the SIM card, the method according to the invention can be used to delete digital data, display it on the screen of the mobile device and modify it. This method can also be used to obtain information concerning various parameters and/or attributes about the said digital data and/or the SIM card as such, for example by displaying the names or statuses of the applets already stored in the SIM card, the memory space available in the SIM card, etc.
The method according to the invention does not involve any modification of the hardware implemented (ordinary telephony equipment can be used) and remains fully compatible with current standards whether regarding the transmissions the smartcards (SIM Toolkit technology) or the communications between the smartcards and the circuits of the mobile device, which invoke APDU standards.